Aspect Ratio Calculator
Calculate missing width or height dimensions while keeping the exact aspect ratio of your image or video. Select popular presets for 16:9 widescreen, 4:3 SD, 9:16 vertical video, 4K, and 1080p.
How to Use the Aspect Ratio Calculator
This calculator automatically maintains proportional scaling when resizing images, video clips, or responsive web containers.
- Calculate New Dimensions: Enter your original width (W1) and height (H1). Type a new desired width (W2) to calculate the matching height (H2), or type a new height (H2) to get the corresponding width (W2).
- Find Simplified Ratio: Enter any resolution in W1 and H1 to find its simplified aspect ratio (e.g. 16:9, 4:3, 1:1) and decimal equivalent.
- Preset Buttons: Click quick ratio buttons like 16:9 or 9:16 to automatically load standard proportions.
The Mathematics of Aspect Ratio Calculation
An aspect ratio represents the proportional relationship between a rectangle width and height. It is expressed as W : H.
To reduce any pixel resolution to its simplest whole-number ratio, divide both the width and height by their Greatest Common Divisor (GCD):
Ratio Width = Width / GCD(Width, Height)Ratio Height = Height / GCD(Width, Height)
To calculate a missing dimension while preserving the aspect ratio:
New Height (H2) = New Width (W2) × (Original Height / Original Width)New Width (W2) = New Height (H2) × (Original Width / Original Height)
Standard Digital Video & Image Resolutions Reference
Refer to the standard resolution matrix below when preparing media for YouTube, social platforms, and digital monitors.
| Resolution Standard | Dimensions (Pixels) | Aspect Ratio | Common Use Case |
|---|---|---|---|
| 4K Ultra HD | 3840 × 2160 | 16:9 | 4K YouTube, TV broadcasts |
| 1080p Full HD | 1920 × 1080 | 16:9 | Standard HD video & desktop screens |
| Instagram / TikTok Story | 1080 × 1920 | 9:16 | Mobile vertical video & Stories |
| Instagram Square Post | 1080 × 1080 | 1:1 | Social media feed posts |
| Ultrawide Gaming | 2560 × 1080 | 21:9 | Curved ultrawide monitors |
Frequently Asked Questions
What is an aspect ratio?
An aspect ratio is the proportional relationship between the width and height of an image, video frame, or display screen. It describes the shape of the rectangle rather than its physical size or pixel count.
What aspect ratio is 1920 x 1080?
1920 x 1080 pixels is a 16:9 aspect ratio. Dividing both 1920 and 1080 by their greatest common divisor (120) yields 16 and 9.
What is the difference between resolution and aspect ratio?
Resolution specifies the total number of pixels along the width and height (e.g., 3840x2160 pixels). Aspect ratio specifies the proportion between width and height (e.g., 16:9). Different resolutions like 1280x720, 1920x1080, and 3840x2160 all share the exact same 16:9 aspect ratio.
Which aspect ratio should I use for social media video?
For horizontal YouTube videos and desktop browsing, use 16:9 (1920x1080). For mobile vertical video platforms like TikTok, YouTube Shorts, and Instagram Reels, use 9:16 (1080x1920).
